1. Field of the Invention
This invention relates to a color discrimination system used for detecting an object according to color or for any other purpose.
2. Description of the Related Art
For example, a color discrimination system placed on an automatic transport line of a factory may be used to detect the presence or absence of an object moving on the line or detect a specific object by collating the color of the object moving on the line (measurement target) with the color given to a detection object. One known color discrimination system used for such a purpose is a system which emits light to a measurement target, receives the light reflected by the measurement target or the light penetrating the measurement target for each of different light wavelengths of, for example, red R, green G, and blue B, finds the sum total of the R, G, and B light reception quantities and the ratio of each of the R, G, and B light reception quantities to the sum total, and compares each ratio with the ratio of the light reception quantity for each wavelength preset for a detection object for finding a match degree therebetween, thereby detecting any desired object.
In such a color discrimination system, the range (determination tolerance) of the ratio of the light reception quantity for each wavelength preset as the comparison reference (or the light reception quantity for each wavelength) is set as the maximum value defined by trial and error and the resolution of the system. Generally, the reference value is set in a stable state in which the detection object is placed at a detection position.
In such a reference value setting, the reference value range of the ratio of the light reception quantity for each wavelength is narrow and it is expected that the discrimination capability is enhanced to cope with the narrow range, but the reference value is not easy to set and a malfunction easily occurs due to noise, disturbance light, etc. Since the reference value is set in a stable state, the measurement target needs also be measured in a similar stable state and the color of the moving measurement target can scarcely be discriminated. The recognition color of the color discrimination system used as the base for setting the reference value may be hard to determine because of the measurement environment, the measurement target, etc.